The present invention relates to a mobile terminal, which reduces or interrupts power supplied to a transmitter unit based on the result of comparison of a physical quantity of transmitting voice with a threshold.
A variety of mobile terminals including cellular phones and car phones are used. These terminals in general are equipped with a voice-operated transmitter (VOX) capability. The VOX capability may reduce or interrupt the electric power supplied to a part of transmitter unit during silent period. This period can be determined based on the comparison of the acoustic power of user voice with a threshold (voice power threshold) when the power of user voice is less than the threshold, allowing the terminal to save power consumption during the silent period.
In these mobile terminals, the threshold for determining whether the user voice is present or absent is fixed to a preset value, irrespective of the status of use of the mobile system. When using this mobile terminal, a user may use the terminal with a hands-free microphone attached (hands-free usage), with a headset microphone attached (earphone usage), or with no optional accessory attached (handset usage). The characteristics of voice transmission via the microphone input in these respective hands-free, earphone microphone, and handset are all mutually different from each other in the actual condition of use. Thus, the VOX capability may work well in the handset usage with the fixed threshold, but may not in the hands-free usage.
The silent period may be determined by other methods. The other methods are, for example, a comparison of the power of voice transmission in a unit of time with a voice power differential threshold, a comparison of a specific power band of voice transmission with a power band threshold, a comparison of frequency components of voice transmission with a reflection coefficient, LSP coefficient or the like. However, as long as the thresholds are fixed, the above same problem remains.